1. Field of the Invention
The present invention relates to a turn signal switch device attached to a steering column of a vehicle and used as a direction indicator, and in particular, to a canceling mechanism of returning an operating lever to a neutral position.
2. Description of the Related Art
According to a turn signal switch device, the base end of an operating lever is rotatably supported to a housing integrated with a steering column and the tip of the operating lever rotates to a direction indicating position between the right and the left in a neutral position to turn on and off lamps for a left turn signal and a right turn signal. According to the above-mentioned turn signal switch device, in order to maintain the operating lever to be in three positions of the right and left direction indicating positions and the neutral position, a cam surface is provided on the internal surface of the housing, and a driving body engaged with the cam surface is provided in the operating lever with a spring inserted thereinto. Also, when a handle is rotated in a direction reverse to the indicating direction, in a state where the operating lever is rotated to a direction indicating position between the right and the left, a canceling mechanism for automatically returning the operating lever to the neutral position is attached to the turn signal switch device (refer to the patent document).
The structure of the conventional turn signal switch device will now be described with reference to the drawings.
FIG. 6 is an exploded perspective view of the conventional turn signal switch device. FIG. 7 is a bottom view of the canceling mechanism. FIG. 8 is a view illustrating the operation of the canceling mechanism.
In drawings, the turn signal switch device comprises first and second cases 101 and 102 made of synthetic resin, which constitute a housing, an operating lever 103 rotatably supported to the cases 101 and 102, first and second levers 104 and 105 provided on the internal surface of the second case 102, and a torsion spring 106 that applies elastic force to a direction where the first lever 104 protrudes from the second case 102. To be mentioned later, the operating lever 103 includes an operating member 107, a holder 108, and a movable member 109. The first and second cases 101 and 102 are integrated with each other using means such as snap coupling and are fixed to a stator member such as a column cover and a combination switch (not shown).
A V-shaped cam surface 110 is formed inside the first. case 101. A driving body 124 engaged with a holder 108 is provided in the cam surface 110 to slide by the force applied by a spring 125. A print substrate (not shown) and a contact point portion for turning on lamps for a left signal and right turn signal are provided on the bottom surface of the first case 101.
A guide shaft 116 and a spindle 117 are provided on the internal surface of the second case 102 to be erected on the same line. The first lever 104 and the second lever 105 are rotatably provided in the guide shaft 116 and the spindle 117, respectively. The first lever 104 and the second lever 105 are rotatably connected to each other. A boss 119 into which a torsion spring 106 is inserted is provided.
Elongated apertures 104a and 104b and a spring receiving portion 104c are provided in the first lever 104. The elongated aperture 104a rotates and slides along the guide shaft 116 and the guide shaft 116 is inserted into the elongated aperture 104a. An abutment portion 104d and a cam portion 104e protrude from the front and in the rear of the first lever 104, respectively.
A first opening 121 and a second opening 122 and a hole 105a rotatably and axially supported to the spindle 117 are provided in the second lever 105. A protrusion 105c and a connecting pin 105d are provided in the tip of the second lever 105. The connecting pin 105d is inserted into the elongated aperture 104d. The tip of the second lever 105 overlaps the first lever 104.
The torsion spring 106 has an arm 106c that extends in a cantilever shape. The arm 106c is engaged with the spring receiving portion 104c of the first lever 104. Elastic force is applied to the first lever 104 in the longitudinal direction of the elongated apertures 104a and 104b by the torsion spring 106.
The operating member 107 is fixed to the base of the operating lever 103, and holder 108 is snapped. A mountain-shaped cam surface 108c is provided in the tip of the top surface of the holder 108. The cam portion 104e of the first lever 104 faces the cam surface 108c. A pair of spindles 108d and 108e protrude from both top and bottom surfaces of the holder 108 and are fitted into the first and second cases 101 and 102.
The movable member 109 is inserted into an opening 108g of the holder 108, is forced by the spring 125, and is pivotally supported to the holder 108. A receiving portion 109e that reaches inside the second opening 122, protrudes from the top surface of the movable member 109. The receiving portion 109e slidably abuts on a curved portion 122a that protrudes from both edges of the opening 122 to the inside of the opening 122.
The first driving body 124 is slidably supported on the front end of the holder 108. The spring 125 is inserted between the first driving body 124 and the movable member 109. The tip of the first driving body 124 is pressed against the cam surface 110 of the first case 101 by the elastic repulsive force of the spring 125.
As mentioned above, the operating member 107 and the holder 108 are rotatably connected to and are fixed to the operating lever 103. The holder 108 and the cases 101 and 102 are rotatably connected to the spindles 108d and 108e, respectively.
The operation is described with reference to FIG. 8. When the operating lever 103 is in the neutral position, the first driving body 124 is maintained in the center of the cam surface 110. At this time, the cam portion 104e of the first lever 104 abuts on the apex of the cam surface 108c of the holder 108, such that, as illustrated in FIG. 8(A), the first lever 104 recedes against the force applied by the torsion spring 106 and is positioned outside the rotation orbit of a canceling protrusion 128.
Next, when the operating lever 103 rotates to a direction, the first driving body 124 slides on the cam surface 110 and is locked. At this time, the holder 108 and the movable member 109 rotate to a movement direction and the apex of the cam surface 108c deviates from the cam portion 104e. Thus, as illustrated in FIG. 8(B), the first lever 104 proceeds along the elongated apertures 104a and 104b by the force applied by the torsion spring 106 such that the abutment portion 104d enters the rotation orbit of the canceling protrusion 128.
In this state, when the handle is rotated in a reverse direction, the canceling protrusion 128 collides with the abutment portion 104d of the first lever 104 during a return operation, and the first lever 104 rotates in a clockwise direction around the guide shaft 117, such that the curved portion 122a of the second opening 122 presses the receiving portion 109e of the movable member 109 upward. The pressure is transmitted to the holder 108 through the movable member 109, such that the first driving body 124 deviates from a locking portion of the cam surface 110 and proceeds toward the center, and that the first and second levers 104 and 105 are automatically returned to the neutral position illustrated in FIG. 8(A).
On the other hand, in the state of FIG. 8(B), when a force that prevents the operating lever 103 from being automatically returned is applied, as illustrated in FIG. 8(C), the receiving portion 109e is pressed toward the curved portion 122a by the component force of the second lever 105 in a rotation direction, and the movable member 109 pivots against the elastic repulsive force of the spring 125, such that the first and second levers 104 and 105 can rotate without being disturbed by the receiving portion 109e. 
[Patent Document 1]
Japanese Unexamined Patent Application Publication No. 2001-6495
However, according to the above-mentioned conventional turn signal switch device, a torsion spring is used as an elastic member for applying force to a lever toward the rotation orbit of a canceling protrusion. Thus, there is a first problem in that it is necessary to secure a large space for providing the torsion spring, such that it is difficult to miniaturize the turn signal switch device.